Avoid adding .root to a file ending in .rntpl in ConfigBuilder

This was uncovered in the RNTUPLE IBs.

Author: Dr15Jones

Configuration/Applications/python/ConfigBuilder.py

@@ -622,7 +622,7 @@ def _addOutputUsingOutputDefinition(self):
                 defaultFileName=defaultFileName.replace('.rntpl','_in'+theTier+'.rntpl')
 
             theFileName=self._options.dirout+anyOf(['fn','fileName'],outDefDict,defaultFileName)
-            if not theFileName.endswith('.root'):
+            if not theFileName.endswith('.root') and not theFileName.endswith('.rntpl'):
                 theFileName+='.root'
 
             if len(outDefDict):